Variable speed soot blower



Jan. 25, 1966 J. R. SALTZ 3,230,568

VARIABLE SPEED SOOI BLOWER Filed April 20, 1964 3 Sheets-Sheet 2INVENTOR.

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Jan. 25, 1966 .1. R. SALTZ 3,230,568

VARIABLE SPEED SOOT BLOWER Filed April 20, 1964 3 Sheets-Sheet 5INVENTOR Z 7? 64/2 2.

United States Patent 3,230,568 VARIABLE SPEED SOOT BLOWER John R. Saltz,Lancaster, Ghio, assignor to Diamond Power Specialty Corporation,Lancaster, Ohio, a corporation of Ohio Filed Apr. 20, 1964, Ser. No.363,330 6 Claims. (Cl. 15-317) The present application is acontinuation-in-part of my prior copending United States patentapplication Serial No. 222,369, filed September 10, 1962, now abandoned,for Variable Speed Soot Blower, and assigned to the same assignee as thepresent invention.

The present invention broadly relates to heat exchanger apparatus, andmore particularly to improvements in apparatus for cleaning the heatexchanger surfaces of high pressure steam boilers and the like. Morespecifically, the present inevntion is applicable to an improvedcleaning mechanism commonly referred to as a soot blower of the longtravel type which incorporates means therein for effecting a controlledvariation in the relative speed of translation and rotation of a lancetube incorporating nozzles therein for discharging a pressurized blowingmedium against the heat exchanger surfaces to be cleaned.

Soot blowers of the long travel or long retracting type, to which thepresent invention is applicable, are in widespread use in various typesof heat exchanger apparatus for providing periodic cleaning of slag andsoot deposits from the heat exchanger surfaces maintaining optimumthermal efficiency thereof. conventionally, a plurality of soot blowersare employed which are disposed at preselected intervals along the heatexchanger apparatus and are operated singly or in multiples forproviding an automatic sequentially phased cleaning operation.

Soot blowers of the so-called long travel type are adapted to be mountedexteriorly of the heat exchanger apparatus and are provided with a lancetube incorporating nozzles in the forward end portion thereof which ismovable to and from a retracted position wherein the forward end portionof the lance tube is positioned in a wall port and out of contact withthe hot combustion gases to a projected position disposed within theheat exchanger apparatus. Conventionally, the lance tube is rotatedduring its projecting and retracting travel and a pressurized blowingmedium such as steam or air, for example, is discharged through thenozzles and impinges against the heat exchanger surfaces effecting theremoval of deposits therefrom. The efiicency of the cleaning actionachieved is determined to a large extent by the uniformity of coverageof the heat exchanger surfaces by the blasting of cleaning mediumdischarged through the nozzles. At the same time, it is desirable tominimize the length of time that the lance tube is projected into thefurnace in which position it is subjected to the hot combustion gaseswhich promote deterioration and wear thereof effecting a shortening ofits useful life.

In order to provide substantially uniform coverage of heat exchangersurfaces, it has heretofore been proposed to employ a lost motion devicein a long retracting type soot blower effecting a displacement in thephase of the helical blowing pattern discharged from the nozzles in thelance tube during its projecting and retracting travel. In view of theoutward pressure exerted against the lance tube by the pressurizedcleaning fluid and the frictional resistance in the soot blower, the useof such lost motion provisions have, in some instances, failed toprovide a phase displacement in the blowing pattern or have providederratic operation resulting in inadequate cleaning of some portions ofthe heat exchanger surfaces traversed thereby.

The increased size of modern high pressure steam boilers has alsonecessitated a corresponding increase in the 3,230,568 Patented Jan. 25,1966 length of the lance tube and the length of travel thereof toprovide the necessary cleaning coverage of the heat exchanging surfaceswithin the boiler. The increased length of the lance tube has imposedrestrictions on the speed of rotation thereof to prevent lance tube whipnecessitating a corresponding reduction in the speed of translationthereof and the necessity of subjecting the lance tube to increasedperiods within the furnace chamber. The necessity of reducing the speedof rotation of the lance tube with a corresponding reduction in thespeed of translation thereof in order to achieve a uniform cleaningpattern, also, has increased the length of the operating cycle anddecreased the efficiency and flexibility of the cleaning operation.

It is, accordingly, a principal object of the present invention toprovide an improved variable speed long travel type soot blower which ismore flexible and versatile and which overcomes the disadvantages andproblems associated with soot blowers of similar type heretofore known.

Another object of the present invention is to provide an improvedvariable speed soot blower which provides for a controlled positivechange in the pitch of the helical blowing pattern achieved during theprojecting travel and the blowing pattern achieved during the retractingtravel of the lance tube during a cleaning operation.

Still another object of the present invention is to provide an improvedvariable speed soot blower which enables a controlled regulation of thespeed of the projecting movement of the lance tube in comparison to theretracting speed thereof in combination with the speed of rotation ofthe lance tube enabling optimum cleaning of the heat exchanger surfaceswithin a shorter time period providing thereby greater efliciency andversatility of the cleaning operation and enhancing the useful life ofthe soot blower.

A further object of the present invention is to provide an improvedvariable speed long travel type soot blower which incorporates powertransmission means therein providing a preselected variation in therelative speed of rotation and translation of the lance tube during itsprojecting and retracting travel into and out of the heat exchangerapparatus.

A still further object of the present invention is to provide animproved variable speed soot blower of the long travel type which is ofsimple design, durable operation, economical manufacture, and whichrequires minimal service and maintenance.

The foregoing and other objects and advantages of the present inventionare achieved 'by employing a single reversible power source operativelyconnected to the lance tube of a long travel type soot blower which uponreversal in the direction of driving rotation is effective through powertransmission means for effecting a positive controlled variation in therelative speed of translation and rotation of the lance tube overcomingthe problem of lance whip and providing for a positive change in thepitch of the helical cleaning pattern assuring uniform deslagging of theheat exchanger surfaces within a mini mal time period.

Other objects, features, and advantages of the present invention willbecome apparent from the subsequent description and the appended claims,taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a fragmentary side elevation view of a long travel type sootblower mounted exteriorly of a heat exchanger apparatus andincorporating therein a variable speed power transmission constructed inaccordance with one of the embodiments of the present invention;

FIGURE 2 is an enlarged fragmentary side elevation view partly insection of the carriage of the soot blower shown in FIGURE 1;

FIGURE 3 is a transverse vertical sectional view of the carriage drivemechanism of the soot blower shown in FIGURE 2 and taken along the line3-3 thereof;

FIGURE 4 is a schematic perspective view of the relationship of thecomponents of the variable speed power transmission incorporated in thesoot blower shown in FIGURES 1-3;

FIGURES 5 and 6 are side elevation views partly in section of thevariable speed power transmission and the arrangement of typicaloverrunning clutches for effecting a change in the relative speed ofrotation and translation of the lance tube of the soot blower shown inFIGURE 1;

FIGURE 7 is a schematic perspective view of an alternate satisfactoryembodiment of the present invention providing for variations in thespeed of rotation of the lance tube between its projecting andretracting travel at a constant speed of translation; and

FIGURE 8 is a schematic perspective view of still another alternatesatisfactory embodiment of the present invention illustrating a variablespeed power transmission providing for both a change in the speed ofrotation and translation of the lance tube between its projecting andretracting travel.

Referring now in detail to the drawings and as may be best seen inFIGURE 1, a typical long travel type soot blower is illustrated to whichthe present invention is applicable. As shown in FIGURE 1, the sootblower comprises a longitudinally extending beam 10 which is supportedby a suitable framework 12 in a position exteriorly of a wall 14 of aheat exchanger apparatus provided with a wall port 16 therethrough. Acarriage 18 is movably mounted on the beam 10 and is movable therealongto and from a retracted position as shown in FIG- URE 1 to an advancedor projected position in which the carriage is disposed on the right endportion of the beam as viewed in FIG-URE l. A lance tube 20 is rotatablymounted on the carriage 18 and extends longitudinally of the beam 10having the forward end portion thereof rotatably and movably supportedin a front support or roller bracket 22 connected to the forward end ofthe beam 10. The lance tube 20 is shown in FIG- URE 1 in the fullyretracted position wherein the forward end thereof incorporating one ormore nozzles 24 therein is disposed within the wall port 16 and shieldedfrom the hot combustion gases within the interior of the boiler.Suitable seals (not shown) are conventionally provided for sealing thelance tube 20 within the wall port 16 preventing the escape of anycombustion gases from the interior of the boiler.

The lance tube 20 is movable by the carriage 18 during the projectingand retracting travel thereof from the retracted position as shown inFIGURE 1 to a projected position wherein the nozzle end portion thereofis disposed within the interior of the heat exchanger apparatus. Duringthe lance tubes projecting and retracting travel, the lance tube isrotated and a pressurized blowing medium is discharged from the nozzles24 in the front end thereof in the form of a helix which traverses andimpinges on the heat exchanger surfaces within the boiler effecting theremoval of slag and other extraneous deposits therefrom. Conventionally,the blowing medium is introduced into the lance tube 20 after thecarriage has advanced a predetermined distance from the fully retractedposition so that the nozzles 24 are disposed beyond the wall port 16 anda series of water wall tubes 26 positioned along the interior surface ofthe boiler wall 14 to prevent direct impingement of the pressurizedblowing medium at close range against these surfaces which mightotherwise cause erosion and damage thereto. Similarly, the discharge ofthe pressurized blowing me dium is stopped during the latter portion ofthe retracting travel of the lance tube at a preselected point beforethe fully retracted position is attained.

The supply of the presurized blowing medium to the lance tube 20 isconveniently achieved by means of a feed tube 28. stationarily mountedat its rearward or left hand end as viewed in FIGURE 1 to a supply valve30. The feed tube 28 extends therefrom forwardly and is disposed intelescopic relationship within the interior of the lance tube 20. Thefeed tube 28 extends forwardly from the supply valve 30 to a pointadjacent to the forward end of the beam 10 maintaining continuouscommunication with the interior of the lance tube 20 as the carriage 18moves from the fully retracted to the fully advanced position. Suitableseals (not shown) are incorporated within the carriage 18 for preventingthe escape of any of the pressurized blowing medium from between thefeed tube 28 and the lance tube 20.

The actuation of the supply valve 30 can be satisfactorily achieved inany one of a number of conventional techniques and is preferablymechanically actuated through an actuator 32 adjustably positioned onthe carriage 18 which is operative to engage and pivot a cam 34pivotally mounted on the beam 10 to which linkage 36 is connected forselectively opening and closing the supply valve 30 when the carriagemoves a preselected distance from the fully retracted position orreturns to a preselected position during its retracting movement fromthe fully retracted position. The supply valve 30 is connected to asuitable supply pipe 38 which in turn is connected to a header (notshown) to which each of the remaining soot blowers is similarlyconnected. The supply valve 30 can also be electrically or remotelyactuated either in response to the travel of the carriage 18 or by anoperator in the central control room.

The advancement of the carriage 18 and the translation of the lance tube20 to and from the retracted position to a projected position and thesimultaneous rotation of the lance tube can be achieved by suitablereversible motor means such as a fluid actuated motor or an electricmotor 40 as specifically shown in the drawings. The reversible motormeans may be mounted directly on the carriage 18, as shown in thedrawings, and electrical energy or a pressurized driving fluid suppliedthereto by a suitable flexible conductor or conduit as the case may be.Alternatively, the reversible motor means can be stationarily mountedeither at the forward end or at the rearward end of the soot blower andprovided with an elongated power transmission shaft of an irregularconfiguration such as a square shaft, for example, which is slidinglycoupled to a driven member for rotating a shaft on the carriage. Ineither case, the reversible motor means is driven in one directionduring the projecting movement of the carriage and lance tube and isdriven in the opposite direction during the retracting movement thereof.

In the specific embodiment shown in FIGURE 1, the electric motor 40 isenergized either manually or remotely by the operator or in accordancewith an automatic sequentially phased control system which provides forautomatic operation of each of the soot blowers in a preselectedoperating sequence to provide optimum cleaning of the heat exchangersurfaces consistent with the accumulation of slag deposits thereon. Inthe arrangement shown in FIGURE 1, energization of the electric motor 40effects forward movement of the carriage toward the projected position.When the fully projected position is attained, the carriage 18 or asuitable actuator thereon, trips a forward travel limit switch LS1mounted on the forward end of the beam 10 which signals the controlcircuit effecting a reversal in the direction of rotation of theelectric motor whereby the carriage 18 commences its retractingmovement. When the carriage 18 attains the fully retracted position, arearward travel limit switch LS2 is tripped by the carriage or anactuator thereon deenergizing the electric motor 40 whereby the carriagestops and is in position for the next operating cycle.

The mode of driving the carriage along the beam 10 can be suitablyachieved by a sprocket drivingly mounted on the carriage engageable witha longitudinally extending chain; by a rotatably driven' lead screwextending the length of the beam and the like; and preferably by a rackand pinion driving arrangement as illustrated in the exemplaryembodiment shown in the drawings. As will be best seen in FIGURES 2 and3, the carriage 18 comprises a gear box or housing 42 incorporating apair of trolley brackets 44 along each side thereof for movably andguidably mounting the carriage 18 on the beam 10. As shown in FIGURE 3,a track plate 46 is rigidly aflixed to the lower flange of the beam 10and projects laterally of the side edges thereof against which an upperroller 48 rotatably mounted on each of the trolley brackets 44 isdisposed in rolling bearing contact. A flanged roller 50 rotatablymounted on each of the trolley brackets 44 is disposed in rollingbearing contact along the underside of the edges of the track plate 46with the flanged rims thereof disposed in overlying bearing contact withthe side edges of the track plate providing lateral guidance of thecarriage during its movement therealong.

The motor 40 is securely fastened to the underside of the housing 42 andis provided with an elongated output shaft 52 on which suitable pulleysor sprockets are mounted. A driven shaft 54 is rotatably mounted andsupported within the housing 42 on which a worm 56 is rotatably fixedsuch as by suitable keys or splines. The worm 56, as shown in FIGURES 2and 3, is disposed in constant meshing relationship with a worm wheel 58which is keyed or splined to a cross shaft 60 which is rotatablysupported in roller bearings 62 in the trolley brackets 44 and a ballbearing 64 supported by a gear box cover 66.

A pinion gear 68 is keyed or splined to the cross shaft 60 in a positionbetween the flanged rollers 50 and is disposed in constant meshingrelationship with a rack 70 affixed to the underside of the track plate46. The rack 70 extends centrally and longitudinally of the beam 10 andfor substantially the entire length thereof. Accordingly, the rotationof the worm 56 in one direction will effect movement of the carriage 18in one direction and upon reversal of the direction of rotation of theworm 56, the carriage correspondingly will reverse direction.

Rotation of the driven shaft 54 and the worm 56 thereon is achieved inthe specific embodiment illustrated in FIG- URES 1-6 by a pair of chainand sprocket transmissions 72, '74 coupled between the output shaft 52and the driven shaft 54. The chain and sprocket transmission 72 isoperative to drive the driven shaft 54 when the electric motor 481srotated in one direction and the chain and sprocket transmission 74 isoperative to drive the driven shaft 54 when the electric motor is drivenin the opposite direction. Alternate suitable transmission means such asgears, belts and pulleys, friction drives, and the like, can besatisfactorily employed in lieu of the specific chain and sprockettransmission shown in the drawings.

The chain and sprocket transmission 72 comprises a driving sprocket 72acoupled to the output shaft 52 and a driven sprocket 72b coupled to thedriven shaft 54. A chain 76 is trained around the sprockets 72a, 72bdrivingly connecting the sprockets together. The sprocket 72a isdrivingly coupled to the output shaft 52tthrough .a suitable clutch 78of the exemplary type shown in FIGURE 6 which is adapted to engage theoutput shaft when it is driven in one direction and to disengage theoutput shaft when it is driven in the opposite direction. The clutch 78as shown comprises a ratchet wheel 80 keyed to the output shaft 52 ofthe motor which is enclosed within an annular housing 82 connected tothe sprocket 72a on which a pair of sprags or pawls 84 are mounted andbiased toward an engaging position with the ratchet wheel 80.Accordingly, when the output shaft 52 is driven in a counterclockwisedirection as viewed in FIGURE 6, the pawls 84 engage the ratchet wheel80 driving the housing '82 and the sprocket 72a in a counterclockwisedirection whereupon the worm 56 is driven so as to effect advance- 6ment of the carriage from the retracted position to the projectedposition.

Similarly, the chain and sprocket transmission 74 comprises a sprocket74a and a sprocket 74b which are drivingly coupled together by a chain86 trained therearound. The sprocket 74b is keyed to the driven shaft 54and the sprocket 74a is drivingly coupled to the output shaft 52 througha clutch 88'which is operable to engage the output shaft 52 and thesprocket 74a when the output shaft 52 is driven in a clockwise directionas viewed in FIGURE 5. The clutch 88 may be of any of the types wellknown in the art which enables a relative overrunning of the sprocket74a, and the output shaft 52 when the output shaft 52 is driven in acounterclockwise direction as occasioned during the projecting travel ofthe lance tube. In the exemplary arrangement as diagrammaticallyillustrated in FIGURE 5, the clutch 88 is of the fluid magnetic typewell known in the art and comprises a driving impeller 90 coupled to theoutput shaft 52 and a driven impeller 92 which is connected to thesprocket 74a. An annular chamber 93 formed between the vaned drivingimpeller 90 and vaned driven impeller 92 is filled with a suitablemagnetic fluid indicated at 94 which conventionally contains magneticparticles and which is of a viscosity to enable relative rotativemovement between the two impellers when in a non-magnetized state. Amagnetic coil 25 is positioned around the annular chamber 93 and uponenergization thereof effects substantial solidification of the magneticfluid 94 in a corresponding driving connection or lockup between thedrive impeller 90 and the driven impeller 82.

In lieu of the magnetic fluid clutch illustrated in FIG- URE 5,alternative satisfactory magnetic disk type clutches can be employed ofthe types well known in the art such as the types illustrated in KentsMechanical Engineers Handbook, 12th edition, published by John Wiley &Sons, Inc., of New York, New York, and disclosed in chapter 15, pages 34and 35. In the exemplary fluid-type magnetic clutch illustrated inFIGURE 5, electrical energy can be conveniently supplied to the magneticcoil through the electrical connection provided by a pair of brushcontacts positioned in electrical contact with a pair of collector rings(not shown) on the output shaft 52 in a manner well known in the art.The energization of the magnetic coil 95 can be achieved in response tothe tripping of forward travel limit switch LS1 which through thecentral control circuit as hereinbefore described is operative to effecta reversal in the direction of rotation of the drive motor 40.Deenergization of the magnetic coil 95 can be achieved in response tothe tripping of rearward travel limit switch LS2 when the carriage andlance tube attain the fully retracted position which concurrentlyeffects the deenergization of the reversible drive motor 40 in a mannerpreviously described. In accordance with this arrangement, when theoutput shaft is driven in, a counterclockwise direction, the drivenshaft 54 and the worm 56 thereon is driven by the transmission 72,during which time the magnetic clutch -88 of the transmission 74overruns and subsequently upon reversal of the direction of rotation ofthe output shaft to a clockwise direction in response to the tripping oflimit switch LS1, the transmission 74 drives the driven shaft 54 duringwhich time the transmission 72 overruns. It will also be appreciatedthat both the clutch 78 and clutch 88 may be of the magnetic type whichare suitably controlled by therespective tripping of forward andrearward travel limit switch LS1 and LS2, respectively.

It will also be understood that the clutches 78 and 88 can be mounted onthe driven shaft 54 and the sprockets 72b, 74b thereon to provide thesame action as achieved through the arrangement shown in the drawings.Additlonally, alternate suitable clutch mechanisms which are operativeto engage in onedirection and to be disengaged upon reversal of thedirection of rotation can be employed in lieu of the exemplary clutchesshown.

The speed of rotation of the driven shaft 54 is established by theratios of the transmissions 72, 74 at a constand motor speed. Inaccordance with the preferred form of the present invention and as bestshown in FIG- URES and 6, the ratio between the diameters of thesprockets 72a, 72b of the transmission 72 is substantially unity wherebythe lance tube is rapidly advanced from the retracted position to theprojected position. On the other hand, the ratio between the sprockets74a and 74b is less than unity whereby the lance tube is retracted moreslowly during its movement from the projected position to the fullyretracted position. In accordance with this arrangement, the lance tubeis rapidly advanced into the interior of the heat exchanger apparatus,effecting partial cleaning during this movement and thereafter iswithdrawn slowly providing a more extensive cleaning. This arrangementminimizes the duration of time during which the lance tube is exposed tothe hot combustion gases.

The lance tube 20 is rotated simultaneously with its translatorymovement and this can be conveniently achieved by the drivingrelationship between a sprocket 96 mounted on the output shaft 52 of thereversible electric motor 40 as shown in FIGURES 1, 2 and 4 and a drivensprocket 98 affixed to the lance tube 20 about which a drive chain 100is trained. The lance tube 20 will, accordingly, rotate at the samespeed during its projecting and retracting travel. In view, however, ofthe differences in the speed of the advancing and retracting movement ofthe lance tube, a positive predetermined change in the pitch of thehelical blowing pattern of the blowing medium occurs as it is dischargedfrom the nozzles 24 in the forward end of the lance tube 20. As shown inFIGURE 4, the helical pattern of the blowing medium discharged throughthe nozzle 24 during the projecting travel of the lance tube as shown insolid lines is of a greater pitch than the helical blowing patternindicated in dotted lines obtained during the retracting travel of thelance tube. This change in pitch in the helical blowing pattern assuresthat uniform coverage of the heat exchanger surfaces is obtained duringthe traversing movement of the lance tube during a blowing operation.

Alternate satisfactory arrangements for providing a positive change inpitch between the helical blowing patterns during the projecting andretracting travel of the lance tube are illustrated in FIGURES 7 and 8.Corresponding components of the apparatus shown in FIGURES 7 and 8 aredesignated by the same numerals hereinbefore employed. In the sootblower arrangement shown in FIGURE 7, a variation in the relative speedof rotation and translation of the lance tube and a positive change inpitch of the helical blowing pattern is achieved by providingtransmission means which varies the speed of rotation of the lance tubebetween its projecting travel and its retracting travel at a constantprojecting and retracting speed of translation. In FIGURE 8, on theother hand, a change in pitch is achieved by a change in both the speedof translation and rotation of the lance tube between its retractingtravel and projecting travel.

In the arrangement shown in FIGURE 7, the output shaft 52 of theelectric motor 40 is drivingly connected to the driven shaft 54incorporating the worm 56 thereon by means of a sprocket 102 affixed tothe output shaft and a sprocket 104 affixed to the driven shaft aroundwhich a drive chain 106 is trained. The speed of rotation of the drivenshaft 54 will be the same in both directions of rotation of the outputshaft 52.

The rotation of the lance tube 20, as shown in FIG- URE 7 during theprojecting travel thereof, is achieved through a chain and sprockettransmission 108 including a sprocket 108a coupled by an overrunningclutch 110 to the output shaft of the motor and a driven sprocket 10811affixed to the lance tube about which a chain 112 is trained. Rotationof the lance tube during the retracting travel therof is achieved by achain and sprocket transmission 114 comprising a driving sprocket 114acoupled by an overrunning clutch 116 to the output shaft 52 and a drivensprocket 1141) connected to the lance tube 20 about which a drive chain118 is trained. In the specific arrangement shown, the ratios of thetransmissions 114 and 108 are such that the lance tube rotates morerapidly during the retracting stroke than during the projecting travelproviding a helical blowing pattern during the projecting travel asshown in solid lines and during the retracting travel as shown in dottedlines which are of diflferent pitch.

The arrangement shown in FIGURE 8 comprises a combination of thetransmission mechanism as shown in FIGURES 4 and 7. Rapid outwardmovement of the lance tube is achieved by a chain and sprockettransmission 120 including a sprocket 120a coupled to the output shaft52 of the electric motor 40 by a clutch 122 and a sprocket 120bconnected to the driven shaft 54 and around which a drive chain 124extends. A slower retracting travel of the lance tube 20 is achieved bya transmission 126 comprising a sprocket 126a coupled to the outputshaft 52 by a clutch 128 and a sprocket 126b connected to the drivenshaft 54 and around which a drive chain 124 extends. A slower retractingtravel of the lance tube 20 is achieved by a transmission 126 comprisinga sprocket 126a coupled to the output shaft 52 by a clutch 128 and asprocket 126k connected to the driven shaft 54 and around which a drivechain 130 is trained.

Similarly, rotation of the lance tube at a relatively slow speed duringits projecting travel is achieved through a transmission 132 including asprocket 132a coupled to the output shaft 52 by a clutch 134 and asprocket 1321) connected to the lance tube 20 around which a chain 135is trained. Rotation of the lance tube during its retracting travel at arelatively higher speed is achieved through a transmission 138 includinga sprocket 138a coupled to the output shaft 52 by a clutch 140 and asprocket 13812 connected to the lance tube around which a chain 142 istrained.

By controlling the relative ratios of the transmissions 120 and 126 foradvancing and retracting the lance tube and the relative ratios of thetransmissions 132 and 138 for rotating the lance tube, the optimumcombination of lance tube travel and rotation can be achieved providingfor a positive pitch change in the helical blowing pattern between theprojecting travel as shown in solid lines in FIGURE 8 and the retractingtravel as shown in dotted lines consistent with the specific nature anddisposition of the heat exchanger surfaces to be cleaned.

While it will be apparent that the preferred embodiments of theinvention disclosed are well calculated to fulfill the objects abovestated, it will be appreciated that the invention is susceptible tomodification, variation and change without departing from the properscope or fair meaning of the subjoined claims.

What is claimed is:

1. A soot blower comprising guide means, a carriage movably mounted onsaid guide means, a lance tube including nozzles in the forward endportion thereof rotatably mounted on said carriage and movable therebyto and from .a projected position and a retracted position, means forsupplying a pressurized blowing medium to said lance tube for dischargethrough said nozzles, a reversible motor, means drivingly connected tosaid motor for rotation of said lance tube in one direction and in anopposite direction in response to rotation 'of said motor in onedirection and in an opposite direction, first transmission meansengageable with said motor in response to rotation thereof in onedirection for moving said carriage and said lance tube toward saidprojected position, second transmission means engageable with said motorin response to rotation thereof in the opposite direction for movingsaid carriage and said lance tube toward said retracted position at aspeed of translation different from the speed of translation during theprojecting travel providing a positive change in the pitch of thehelical blowing pattern discharged from said nozzles.

2. A soot blower comprising guide means, a carriage movably mounted onsaid guide means, a lance tube including nozzles in the forward endprti0n thereof rotatably mounted on said carriage and movable thereby toand from a projected position and a retracted position, means forsupplying a pressurized blowing medium to said lance tube for dischargethrough said nozzles, a reversible motor, means drivingly connected tosaid motor for rotation of said lance tube in opposite directions at thesame speed in response to rotation of said motor in one direction and inan opposite direction, first transmission means including an overrunningclutch engageable with said motor in response to rotation thereof in onedirection for moving said carriage and said lance tube toward saidprojected position, second transmission means including an overrunningclutch engageable with said motor in response to rotation thereof in theopposite direction for moving said carriage and said lance tube towardsaid retracted position at a speed of translation diiferent than thespeed of translation during the projecting travel providing a positivechange in the pitch of the helical blowing pattern discharged from saidnozzles.

3. A soot blower com-prising guide means, a carriage movably mounted onsaid guide means, a lance tube including nozzles in the forward endportion thereof rotatably mounted on said carriage and movable therebyto and from a projected position and a retracted position, means forsupplying a pressurized blowing medium to said lance tube for dischargethrough said nozzles, a reversible motor, means drivingly connected tosaid motor for moving said carriage and said lance tube to saidprojected position in response to rotation of said motor in onedirection and to said retracted position in response to rotation of saidmotor in the opposite direction, first transmission means engageablewith said motor in response to rotation thereof in said one directionfor rotating said lance tube in one direction during its projectingtravel, second transmission means engageable with said motor in responseto rotation thereof in said opposite direction for rotating said lancetube in the opposite direction during the retracting travel thereof at aspeed of rotation different from the speed of rotation during itsprojecting travel providing a positive change in the pitch of thehelical blowing pattern discharged from said nozzles.

4. A soot blower comprising guide means, a carriage movably mounted onsaid guide means, a lance tube including nozzles in the forward endportion thereof rotatably mounted on said carriage and movable therebyto and from a projected position and a retracted position, means forsupplying a pressurized blowing medium to said lance tube for dischargethrough said nozzles, a reversible motor, means drivingly connected tosaid motor for movement of said carriage and said lance tube toward saidprojected position in response to rotation of said motor in onedirection and for movement of said carriage and said lance tube towardsaid retracted position in response to rotation of said motor in theopposite direction and at substantially the same speed of translation,first transmission means including an overrunning clutch engageable withsaid motor in response to rotation thereof in said one direction forrotating said lance tube in one direction during its projecting travel,and second transmission means including an overrunning clutch engageablewith said motor in response to rotation thereof in said oppositedirection for rotating said lance tube in the opposite direction duringits retracting travel at a speed of rotation different from the speed ofrotation thereof during its projecting travel providing a positivechange in the pitch of the helical blowing pattern discharged from saidnozzles.

5. A soot blower comprising guide means, a carriage movably mounted onsaid guide means, a lance tube including a nozzle in the forward endportion thereof rotatably mounted on said carriage and movable therebyto and from a projected position and a retracted position, means forsupplying a pressurized blowing medium to said lance tube for dischargethrough said nozzles, a reversible motor, first transmission meansengageable with said motor in response to rotation thereof in onedirection for moving said carriage and said lance tube toward saidprojected position, second transmission means engageable with said motorin response to rotation thereof in the opposite direction for movingsaid carriage and said lance tube toward said retracted position at adifferent speed of translation from the speed of translation during theprojecting travel thereof, third transmission means engageable with saidmotor in response to rotation thereof in said one direction for rotatingsaid lance tube, and fourth transmission means engageable with saidmotor in response to rotation thereof in said opposite direction forrotating said lance tube at a speed different from the speed of rotationthereof during its projecting travel providing a combined relative speedof rotation and translation of said lance tube which is different duringits projecting and retracting travel and eifecting a positive change inthe pitch of the helical blowing pattern discharged from said nozzles.

6. A soot blower comprising guide means, a carriage movably mounted onsaid guide means, a lance tube including nozzles in the forward endthereof rotatably mounted on said carriage and movable thereby to andfrom a projected position and a retracted position, means for supplyinga pressurized blowing medium to said lance tube for discharge throughsaid nozzles, a reversible motor, first transmission means including anoverrunning clutch engageable with said motor in response to rotationthereof in one direction for moving said carriage and said lance tubetoward said projected position, second transmission means including anoverrunning clutch engageable with said motor in response to rotationthereof in the opposite direction for moving said carriage and saidlance tube toward said retracted position at a speed of translationdifferent from the speed of translation during the projecting travelthereof, third transmission means including an overrunning clutchengageable with said motor in response to rotation thereof in said onedirection for rotating said lance tube during its projecting travel, andfourth transmission means including an overrunning clutch engageablewith said motor in response to rotation thereof in said oppositedirection for rotating said lance tube during its retracting travel at aspeed of rotation different from the speed of rotation during itsprojecting travel providing thereby a combined relative speed oftranslation and rotation which is different during the projecting andretracting travel of said lance tube effecting a positive change in thepitch of the helical blowing pattern discharged from said nozzle.

References Cited by the Examiner UNITED STATES PATENTS 2,441,112 5/1948Hibner et al 15317 2,760,222 8/ 1956 Anderson 153 17 2,883,694 4/1959Hibner et al. 15317 2,932,053 4/1960 McColl 15-317 ROBERT W. MICHELL,Primary Examiner.

WALTER A. SCHEEL, Examiner.

1. A SOOT BLOWER COMPRISING GUIDE MEANS, A CARRIAGE MOVABLY MOUNTED ONSAID GUIDE MEANS, A LANCE TUBE INCLUDING NOZZLES IN THE FORWARD ENDPORTION THEREOF ROTATABLY MOUNTED ON SAID CARRIAGE AND MOVABLE THEREBYTO AND FROM A PROJECTED POSITION AND A RETRACTED POSITION, MEANS FORSUPPLYING A PRESSURIZED BLOWING MEDIUM TO SAID LANCE TUBE FOR DISCHARGETHROUGH SAID NOZZLES, A REVERSIBLE MOTOR, MEANS DRIVINGLY CONNECTED TOSAID MOTOR FOR ROTATION OF SAID LANCE TUBE, IN ONE DIRECTION AND IN ANOPPOSITE DIRECTION IN RESPONSE TO ROTATION, OF SAID MOTOR IN ONEDIRECTION AND IN AN OPPOSITE DIRECTION, FIRST TRANMISSION MEANSENGAGEABLE WITH SAID MOTOR IN RESPONSE TO ROTATION THEREOF IN ONEDIRECTION FOR MOVING SAID CARRIAGE AND SAID LANCE TUBE TOWARD SAIDPROJECTED POSITION, SECOND TRANSMISSION MEANS ENGAGEABLE WITH SAID MOTORIN RESPONSE TO ROTATION THEREOF IN THE OPPOSITE DIRECTION FOR MOVINGSAID CARRIAGE AND SAID LANCE TUBE TOWARD SAID RETRACTED POSITION AT ASPEED OF TRANSLATION DIFFERENT FROM THE SPEED OF TRANSLATION DURING THEPROJECTING TRAVEL PROVIDING A POSITIVE CHANGE IN THE PITCH OF THEHELICAL BLOWING PATTERN DISCHARGED FROM SAID NOZZLES.